CH 15 Acid-Base Titration and pH 15 CH 15 Acid-Base Titration and pH 15.1 Aqueous Solutions and the Concept of pH Recall: acids and bases make hydronium (H3O+) and hydroxide (OH-) ions in aq solns Pure water is an extremely weak electrolyte and undergoes self-ionization

Conductivity measurements H3O+ and OH- in pure water are each only 1.0x10 -7 mol/L Kw=[H3O+ ] [OH- ] Neutral Concentration H3O+ = conc. OH- Acidic Conc. H3O+ > conc. OH- Basic Conc. H3O+ < conc. OH-

Mole ratios to tell H3O+ or OH- Calculating H3O+ & OH- write ionic equation Mole ratios to tell H3O+ or OH- [H3O+][OH- ]= 1.0x10 -14 M2 Don’t forget sig figs! *Link for video*

pH = -log [H3O+] pOH = -log [OH-] pH + pOH = 14.0 Increasing H3O+ means decreasing pH pH is logarithmic function, each unit represents a 10-fold difference; pH 3 is 10x greater than pH 4 pOH = -log [OH-] pH + pOH = 14.0

Calculating pH using [H3O+ ] write ionic equation Mole ratios to tell H3O+ pH = -log [H3O+] *Link for video*

Calculating pH using [OH-] [H3O+][OH−] = 1.0 × 10−14 M2 Solve for [H3O+] pH = -log [H3O+] Problem C

Calculating from pH to [H3O+] Calculating pH using [OH-] pH = -log [H3O+] -pH = log [H3O+] antilog(-pH)= [H3O+] or 1.0 x 10 –pHw = [H3O+] Problem D

15.2 Determining pH and Titrations Acid-base indicators are compounds which change color with changes in pH are organic Act as very weak Bronstead-Lowry acids or bases Change color when accept proton from acid or donate proton to base

pH paper is different from litmus paper! pH paper has multiple indicators (thus color spectrum it can display) pH meter gives reading/measurement from voltage changes of [H3O+]

Titration Used to determine exact concentrations Control addition of solution with known concentration Measure amount of solution of unknown concentration

Recall neutralization Titration is way of determining chemically equivalent amounts of acids and bases End point: when the indicator changes color at end of titration

Standard solution: aka known, has known concentration Primary standard: purified solid solution used to check concentration of known solutions in titration Equivalence point occurs ½ way between 2 points where line curves

Solving M of unknowns Balanced equation Determine moles of acid/base of known Determine moles of solute of unknown used in titration Calculate M of unknown soln